Minden flood planning opinion Heather Sadler

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Planning opinion prepared by EcoVue consultant Heather Sadler for the Township of Minden Hills regarding floodplains.

Text of Minden flood planning opinion Heather Sadler

  • Dear Reeve Reid and Members of Council:

    For the Village of Minden, the spring of 2013 will long be remembered as the spring when the Gull

    River rose up over its banks and flooded the downtown. The devastation that the flood waters

    bring is very real, both in the short term and the longer term. It is one of the few examples of the

    power of the natural environment that still manages to render us almost powerless. Short of piling

    sandbags, there is little we can do except join together to support each other in our time of

    collective need.

    Having said that, there are lessons to learn about how to avoid this level of devastation and

    despair in the future. This paper has been prepared, as a donation to the municipality, to provide

    assistance to the Township of Minden Hills and its residents regarding the flooding that has

    occurred and more importantly, what can be done in the future. We have included some history of

    the known risk of flooding along the Gull River and also provided some guidance with respect to

    planning initiatives which can help the community to prepare for future flooding events. It is hoped

    that the municipality may find this information helpful as it tackles the challenges of managing flood

    prone lands in the village and along the Gull River to the south.

    The paper is based on our professional experience and understanding of flooding hazards in

    general and our familiarity with the village of Minden in particular. As a former Manager of Planning

    and Regulations with the Otonabee Region Conservation Authority in Peterborough, and a

    June 17, 2013 Reeve Reid and Members of Council Township of Minden Hills P.O. Box 359, Minden, Ontario K0M 2K0. Attn:

    Nancy Wright-Laking CAO, Clerk and EDO

    Re: Planning Opinion

    2013 Minden Flood In Support of Flood Damage Relief Efforts

  • Flood Plain Management on the Gull River Township of Minden Hills

    June 12, 2013

    P a g e | 2

    Registered Professional Planner in the Province of Ontario, the undersigned has extensive

    experience in flood plain management and policy. We felt it was important that this perspective be

    shared with the Township of Minden Hills. This paper is our contribution to the Disaster Relief

    initiative. There is no fee for this information and we expect nothing in return. We simply hope that

    the information will assist the municipality with this ongoing issue.

    1. BACKGROUND

    Land use planning policy in the Province of Ontario is quite clear about the manner in which new

    development must be planned to avoid damage from flooding. Protection against damage to

    property and damage to life and limb are key aspects of the Natural Hazards policies set out in the

    Provincial Policy Statement.

    In many ways, these policies grew out of the experiences of Hurricane Hazel. In 1954, Hazel

    struck Canada as an extra-tropical storm, with a death toll in the Toronto area of 81 people.

    Approximately 4,000 homes were destroyed and more than a billion dollars (2009 dollars) in costs

    including economic disruption, the cost of property losses and recovery costs resulted. The effects

    of Hazel in Toronto were unprecedented, as a result of a combination of a lack of experience in

    dealing with tropical storms and the storm's ferocity. Other floods, such as the 1974 Grand River

    flood (CambridgeGalt), the 1961 Timmins storm, and the 1980 Ganaraska River (Port Hope), also

    underscored the vulnerability of communities to extreme flood events. More recently the

    Peterborough floods of 2002 and 2004 have reminded residents in this area that flooding can

    occur at any time and that communities built in the floodplains of rivers are always vulnerable.

    1.1 History of Flooding In Minden

    Based on historical photos and recollections of long-time residents of Minden, it is clear that the

    flooding experienced this past spring is typical of serious flood events affecting the Gull River and

    the village of Minden. According to historic records, the Gull River has overflowed its banks in the

    village of Minden on a number of occasions. Flooding is documented as far back as 1913, 1928,

    and 1929, as well as 1943, 1950, and 1983. It was as a result of the 1983 flooding, that measures

    were initiated to better understand the flooding risk along the Gull River and to manage this risk

    more effectively.

  • Source: Spring 1943 - Between Anson Street and Bobcaygeon Road, southwest from Peck Street - courtesy of the FRDP Public Information Flood Risk Map for the Gull River, 1988

  • Spring 1951 - Flooding on Peck Street in Minden, looking northwest towards the Gull River- courtesy of the FRDP Public Information Flood Risk Map for the Gull River, 1988

  • Source: - May 1983 - flooding ON Anson Street in Minden,looking north courtesy of the FRDP Public Information FloodRisk Map for the Gull River, 1988

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    2. THE CANADA-ONTARIO FLOOD DAMAGE REDUCTION PROGRAM

    In some cases flooding can be managed by attempting to modify natural systems, through dams,

    dykes and channelization works. This approach is very costly and does not guarantee that a flood

    event can be controlled. In 1975, the federal government initiated Flood Damage Reduction

    Program (FDRP), through Environment Canada, to curtail escalating disaster assistance payments

    in known flood risk areas, as well as the reliance on costly structural measures.

    The FDRP consists of three steps. The first is to identify and map flood risk areas. The second is

    to designate these areas as being at risk of flooding by publishing Public Information Flood Risk

    Maps which show the extent of flooding. The third step is to apply policies to discourage future

    development in flood prone areas which have been identified through the program. Once a flood

    risk area is mapped and designated both the federal and provincial governments agree not to build

    or support (e.g., with a financial incentive) any future flood vulnerable development in those areas.

    New development is not eligible for disaster assistance in the event of a flood.1

    Local governments also play an important role in flood plain management, since they are generally

    responsible for land use planning and regulation of new development. The FDR agreements

    require that local authorities be encouraged to zone according to flood risk in designated areas. In

    some provinces, the local levels of government are required to incorporate flood hazard

    information into municipal planning through official plans, zoning bylaws, subdivision plans, and

    flood and fill regulations.

    2.1 The Minden FDRP

    In the case of Minden, flood plain mapping was completed for the Gull River in 1988. This mapping

    was prepared under the Canada-Ontario Flood Damage Reduction Program. The flood risk areas

    were determined through hydrologic and hydraulic analyses conducted in 1986 by Paragon

    Engineering Limited.2 The analysis of the extent of the flood risk area associated with the Gull

    River was calculated on the basis of the most severe thunderstorm on record for the area. The

    FDRP mapping for the Gull River extends from the dam at the bottom end of Minden Lake to the

    1 http://www.ec.gc.ca/eau-water Environment Canada - Flood Damage Reduction Program 2 Public Information Flood Risk Information Map Gull River Township of Anson, Hindon & Minden and the Township of Lutterworth. Canada-Ontario Flood Damage Reduction Program, 1988.

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    outflow of the river into Gull Lake at Sandy Bay (see Figure 1 below).. Detailed mapping of the

    floodplain was provided to the municipality through the FDRP program. Copies are also available

    through MNR.

    Source: FDRP Public Information Flood Risk Map - Gull River

    2.1.1 Calculating the extent of the flooding hazard

    Paragon Engineering would have used sophisticated computer models to determine the extent of

    flooding that would occur on the Gull River, based on established records of the areas most

    severe flood event. In many areas, the 1:100 year storm event is used as the basis for modelling

    the anticipated extent of flooding from a major storm event. For the Gull River, the historic event

    used to calculate flooding is the Timmins Storm, which occurred in August of 1961. The flooding

    resulting from the Timmins Storm exceeded that of the one hundred year flood, often referred to as

  • Flood Plain Management on the Gull River Township of Minden Hills

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    the 1:100 year flood event. The 1:100 year flood is based on an analysis of precipitation, snow

    melt, or a combination of the two. The chance of it occurring is once in one hundred years or

    conversely a 1% chance of happening in any given year. Contrary to popular opinion (gamblers

    fallacy), this does not mean that such an event will only happen once every one hundred years. In

    the City of Peterboroughs case, two one hundred year floods occurred within two years (2002

    and 2004). As such, municipalities and landowners must understand that areas within a floodplain

    are always susc